In the oil and gas sector, for example, wells are abandoned because they are no longer needed to support oil and gas development or because an operator's mineral lease has expired.
There are a number of requirements to ensure that an abandoned well is safe and does not damage the surrounding environment. Each jurisdiction may have different requirements. For example, in Alberta, Canada, under Directive 020: Well Abandonment, the Alberta Energy Regulator has set strict requirements for environmental protection and public safety in areas around abandoned wells. However, many jurisdictions require that abandoned wells be sealed and at least partially filled.
There are a number of techniques available to the industry in regards to abandoning wells that are deemed to be past their life cycle. The current abandonment procedure can use coiled tubing, a service rig with jointed tubing, or wireline to deploy the abandonment plug and cement.
The procedure focused on here is using tubing to perform the abandonment. In the past, the first step would be to run a casing scraper to remove any build up of debris on the production casing. The scraper will remove any metal chards as a result of the perforating process that was performed to allow the hydrocarbons to flow into the well bore.
Once the scraper run has been completed, a permanent bridge plug is run into the well bore and set above the perforated zone that is being abandoned. This involves running the bridge plug into the wellbore on a hydraulic setting tool, collar locator, shear subsystem and grapple connector. A hydraulic pressure medium will be pumped activating the hydraulic setting tool thus setting the bridge plug with 30,000 lbs of force. All the equipment would then be removed from the wellbore.
The well bore would be pressure tested before the cementing process. Once a positive pressure test was completed the cementing process can begin. Prior to the running back into the hole, a pump down dart is inserted into the coiled tubing bore along with the spotting tool. A recommended amount of cement is pumped into the coiled tubing. The valve is closed trapping and containing the cement in the coiled tubing. The cementing equipment can now be run back into the wellbore, tagging the bridge plug. Hydraulic pressure medium pumps against the pump down plug which in turn creates pressure causing the valve in the spotting tool to shift, releasing the cement on top of the bridge. Hydraulic pressure is maintained as the bottom-hole assembly is pulled out of the hole and cement is continually pumped. The bottom-hole assembly is then removed from the wellbore.
US 2008/0314591 (Hales et al.) discloses a method of abandoning a well including the steps of: assembling a tool string including a perforating gun interconnected between first and second packer assemblies; conveying the tool string into a wellbore in a single trip; setting the first packer assembly; setting the second packer assembly; firing the perforating gun; and flowing cement into an annulus longitudinally between the first and second packer assemblies.
US 2009/0183875 (Rayssiguier et al.) discloses an apparatus to be lowered in a borehole, comprising: (i) a delivery section for delivering a plugging fluid; (ii) a setting section comprising a longitudinal element and a flexible and permeable sleeve into which the plugging fluid is delivered; and (iii) a disconnect mechanism to allow the delivery section to be disconnected from the setting section, characterized in that the flexible sleeve is connected by at least one floating means to the longitudinal element.
US 2015/0275605 (Bennett et al.) discloses a downhole tool including a bridge plug releasably coupled to a casing cutting tool. The bridge plug may be set within a wellbore and the casing cutting tool may be used in a milling or perforating operation during a single downhole trip of the downhole tool.
U.S. Pat. No. 4,423,783 (Haag) discloses a method for plugging a well comprising (1) extending two sets of dogs on a bridge plug for engaging the sides of the well by releasing an expandable means, and (2) releasing a high pressure fluid for triggering and releasing the expandable means for extending the two sets of dogs for securing the bridge plug at the desired depth in the well. A bridge plug for carrying out the method is also disclosed.
U.S. Pat. No. 5,469,918 (Haberman) discloses a device for suspension in a wellbore by means of cable with the device including a cement slurry containment means (such as bailer tube) a bridge plug, and a bridge plug retaining ring.
U.S. Pat. No. 6,454,001 (Thompson et al.) discloses a method and apparatus for plugging a well. The apparatus includes a well barrier which may be connected to a pipe string and lowered into a well to a selected plug location. The barrier is held in place by the pipe string at the selected plug location. The well barrier will engage the well at the selected plug location. A plugging fluid is displaced through the pipe string and is communicated into the well above the barrier. The well barrier will catch the plugging fluid. After the plugging fluid gels sufficiently to support itself in the well, the pipe string which was utilized to lower the well barrier can be disconnected from the well barrier and removed from the well after the plugging fluid has been allowed to set to a sufficient gel strength.
U.S. Pat. No. 6,595,289 (Tumlin et al.) discloses a method and apparatus for plugging a wellbore in a trip saving manner. In one aspect, embodiments comprise a cement retainer disposed on a run-in string and a radially expanded perforating assembly disposed below the cement retainer. In a single run, the apparatus provides for perforating a wellbore and squeezing cement through the perforations and into the surrounding formation.